Remove V8Utilities

- This CL moves extractTransferables() from V8Utilities to SerializedScriptValue, since the method is related to SerializedScriptValue.

- Then removes V8Utilities.{h,cpp}

BUG=339037
R=jochen@chromium.org

Review URL: https://codereview.chromium.org/141893007

git-svn-id: svn://svn.chromium.org/blink/trunk@168375 bbb929c8-8fbe-4397-9dbb-9b2b20218538